


Twins are Dangerous: Seteth

by theflyingpan



Series: Twins_Are_Dangerous_AU [1]
Category: Fire Emblem Series, Fire Emblem: Fuukasetsugetsu | Fire Emblem: Three Houses
Genre: Father-Daughter Relationship, Flayn is the best girl, Fluff, Fluff and Angst, No Smut, Spoilers for most of the game, Twins_Are_Dangerous AU, a bit of angst, and a bit after that, i haven't finished any playthrough so its only up to the five year skip, no beta we die like men, spoilers for Seteth and Flayn's A Support
Language: English
Status: Completed
Published: 2019-08-23
Updated: 2019-08-23
Packaged: 2020-09-25 01:17:07
Rating: General Audiences
Warnings: Creator Chose Not To Use Archive Warnings, Major Character Death
Chapters: 1
Words: 2,643
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/20368249
Author URL: https://archiveofourown.org/users/theflyingpan/pseuds/theflyingpan
Summary: “When Seteth first laid eyes on the twins, his first and immediate thoughts were “Demons”. He immediately felt guilty.”((You can read this as Seteth/Byleth, but I didn’t intend to write it that way. I just wanted to explore his relationship to the twins))





	Twins are Dangerous: Seteth

When Seteth first heard about the twins, it was through Lady Rhea in passing.  
“The students were attacked it seems.” She offhandedly mentioned. He nearly dropped the documents she requested him to bring. The Archbishop didn’t seem to notice. “The heads of the Houses found a group of mercenaries to help fend off the attacks. Apparently an ex-knight of Seiros was one of them.” Rhea explained before sipping more tea. Seteth tried in vain to process the information.  
“That's…a relief” He managed, setting the documents down. “Are they unharmed?” Rhea nodded.  
“It seems that a certain set of siblings were strong enough to ensure the safety of the students. All of them” The Archbishop gave him a knowing look before smiling and standing. “They will be arriving soon, will you join me in thanking them?” It was a strange request, but the mention of ‘_siblings_’ eased Seteth’s worries enough to agree. He wondered what will be waiting for him, as he and Lady Rea waited for their company.

((It wasn’t until much later did Seteth stop to wonder how much Lady Rhea already knew about the siblings, and how much she was hiding from him))

* * *

When Seteth first laid eyes on the twins, his first and immediate thoughts were “Demons”. He immediately felt guilty. Long and old superstitions aside, he tried to get a proper read on the two young adults standing before him, standing on either side of the ex-knight Lady Rhea mentioned. The shorter of the two was female, judging by her <strike>large</strike> chest and longer eyelashes. She wore her hair the same as her brother, with equally messy locks of blue hair falling on her shoulders. She also seemed to be nervous under the combined gazes of himself and the Archbishop. The taller male twin held the same stoic expression as his sister, but with a gaze more sharp than soft. He also held himself like his father: confident and distrusting. He firstly thought he preferred the male twin over the female due to their confidence—but then the Archbishop spoke.  
“So, you must be Jeralt’s children. Might I ask for your names?” Her voice was laced with a touch of motherly sweetness which didn’t go unnoticed by the children in question. The male narrowed his eyes while the female widened hers. After a beat of silence Seteth found his patience wearing thin, but before he could scold them—  
“B-Byleth…” A soft voice called out. All turned to face the speaker: _Byleth_, he presumed, wasn’t looking at them, but rather her hands. She glanced at Lady Rea before dropping her gaze again, nodding a bit to herself.  
“And _your_ name?” Seteth pressed, turning to the still silent male twin. Met with no response, he let himself get angry. “You should at _least_ give the Archbishop your name! It is the _least_ you can do for a woman of her pow-“  
“That is alright Seteth” Rhea stopped him with a knowing smile. “We were just given their names, were we not?” Seteth blinked, confused, as Rea turned to Jeralt. “They are _both_ named Byleth?”  
“Well,” The mercenary chuckled thinly, scratching the back of his head. “Their mother decided on it, and we weren’t expecting twins.”

((If their names were unexpected, then Seteth had no idea what to call the emotion he felt when Lady Rhea offered them a teaching position, or the emotion that followed when the two _accepted_.))

* * *

When Seteth first saw the twins stand confidently without their father, it was when they first addressed their houses. Byleth…well, the female Byleth, had chosen to lead the Black Eagles(a bit of a strange choice in Seteth’s eyes), and her brother chose the Golden Deer (Seteth rolled his eyes, of course he would choose that _schemer_). Hanneman was put in charge of the Blue Lions, and Manuela was put in charge of the infirmary full time. Seteth saw how relaxed the female twin felt in the presence of another strong woman such as Edelgard, and he was already getting headaches just looking at the way Claude draped his arm around male Byleth’s shoulders, whispering a scheme to the professor’s delight. It was going to be a long year.

((Seteth was a bit grateful that Byleth could tame Claude enough to get him to focus in class, and that his sister managed to warm up Edelgard’s somewhat cold personality.))

* * *

When Seteth first saw the twins separated, he had the unfortunate luck of finding the male twin first. Maybe it was the way he had looked at Lady Rea when they first met, with eyes filled with distrust and cold hatred. Maybe it was the way he only spoke in short, sharp sentences laced with an air of arrogance and sass. Maybe it was the way Flayn eyes lit up upon seeing him (although, she would argue over and over, Flyan was just as excited if not more to see the female twin as well). Either way, Seteth and the male Byleth rubbed each other the wrong way, and the two always found themselves seconds away from a screaming match (despite his tendency to stay silent, Byleth was all too eager to argue endlessly with Seteth). Typically, their meetings resulted in any nearby student running across the Monastery to fetch whosoever sibling they could find to break the two up (if it was Flayn, they could only hope that Seteth didn’t direct his anger at any male student who had to drag her by her hands to her brother. If it was Byleth, then at least the students were entertained by the way she could tame her wild twin).  
“_Honestly_ brother, you are nearly as insufferable when it comes to the Professor as when you interrogate my friends!” Flayn had huffed as she pulled Seteth away from his first of many arguments with the male twin, who stayed behind in the training hall to rid himself of his aggression. “_Why_ is it that you dislike him so much?” Flayn turned to give her brother a hard stare, safely away from the man in question.  
“I honestly cannot tell you, Flayn” Seteth sighed and ran a hand over his face, looking away from his sister’s hard glare in an attempt to calm down. It failed, as his heart leaped into his throat at the sight of blue, disheveled hair. Flayn had noticed.  
“That’s just Byleth, the _female_ one, brother” She sighed, as Byleth ran past the two in the direction of the training hall. “Does the mere _thought_ of him set you on edge or something??” Seteth couldn’t say, but this time because his voice had left him. Maybe it was the way she ran: with her face full of worry, her arms swinging to help her run faster, the sweat running down her face. Maybe it was the way he saw the ghost of a loved one in her eyes. Maybe it was the way the normally quiet and soft-spoken professor yelled for her brother in loud worry. Either way, he was suddenly hit with the urge to hold Flyan and ensure himself that his family was alright.

((Seteth later learned that, once she realized that her brother was in no danger, Byleth had given her brother such a scolding that the entire Golden Deer class wouldn’t let it go for a whole month. That made him feel a bit better.))

* * *

When Seteth pleaded for the twins to find his Flayn, he was relieved to see their faces (normally polar opposites or just stoic) morph from genuine fear, to anger then determination. The bolder twin’s hands twitched and reached for the small dagger he had on his person at all times, while the more reserved twin surprised him by suddenly grabbing this face. The nervousness he long learned to associate her with was nowhere to be seen, instead replaced with cold resolve.  
“Breathe, _please_ Seteth” She gently urged him, and Seteth realized he was hyperventilating. There was so much to worry about(secret identities, blood relations, crests), and the panic was suffocating him. But Byleth’s hands grounded him, and he started to breathe normally. A third hand was placed on his right shoulder, and when he looked over he found the other Byleth’s hand gripping him, face hard with dedication.  
“We will find her, unharmed” He assured him, before grabbing his sister’s hand and walking to the door— mind already racing to find any and all traces of the missing girl. Seteth didn’t miss the way the Professor’s hand gripped his sister in a tight vice, arm shaking.

((Seteth was shaking as well, but while he was still worried sick about Flayn, he was confident that the twins wouldn’t return without her))

* * *

When Seteth was reunited with his dear Flayn, she was sleeping peacefully— unaware of the worry he was in the entire month. Byleth had yelled his name with an urgency he never heard before, and when he turned he saw the two running at full speed to him. Byleth had tears in her eyes, and her brother had Flayn in his arms, wrapped in two identical coats, pressed tightly to his body— as if she’d disappear again if he even thought of letting go. The twins nearly ran him over, but when Flayn was returned to his arms, Seteth found he couldn’t be mad. He held his sister, his _daughter_, close, and when he looked up to thank the two he was greeted with tears— from both siblings. He laughed a bit before his own tears mixed with theirs on the cold pavement below them, and the two wasted no second in pulling him into a tight hug.  
((Later, Lady Rhea recalled how she and Jeralt found the four; sitting in the middle of the bridge to the chapel, holding each other as if afraid to let go and watch the other disappear. Jeralt said nothing of that day, but did watch over his kids a bit closer from then on.))

* * *

When Seteth saw the twins walking behind Flayn, he had the same thought she voiced a full minute before her.  
“Professor! Byleth!” Flayn called out, waving them over. “_Please_ accompany us to the beach!” Seteth could practically feel male Byleth’s confusion and female Byleth’s worry at the urgency in Flayn's voice, and quickly cleared things up. He was relieved to find both siblings equally ready to help, the past months’ activities perhaps lending to their lack of hesitance.  
When they arrived at the beach to face the wayward priests and bishops, Seteth was able to assess the situation with Byleth by his side calming him down and pointing out enemies he deemed more dangerous than others. He was also able to mount his Wyvern with confidence as Byleth assured him she’d make sure Flayn didn’t get in danger.  
Later, as Flayn knelt to greet her mother<strike>(the battle over within a few hours with the combined power of at least four powerful crests activating)</strike>, Seteth felt safe enough to confess at least some of his secrets.  
“I almost wish I _didn’t_ know” Byleth sighed, picking up a stray rock and tossing it to the ocean with an unreadable expression on his face. Setheth felt his heart drop and he glanced to the female twin to try and assess the situation, only to see her equally confused. “I miss knowing we were the _cooler_ siblings.” Byleth shrugged, his grin coming back. When Seteth saw Byleth’s face, he laughed harder than he had in a long time.

((“I _like_ Byleth” Flayn suddenly announced over dinner, causing Seteth to choke on his fish and cough up a storm. She slid his glass of water closer within his reach and continued to eat, smiling a bit that was in no way influenced by his reactions. “I think they do a _wonderful_ job connecting with the students and teaching. It’s almost _romantic_, isn’t it brother?”  
“Is that so..?” Seteth forced a smile, wiping his mouth and thinking of all the ways he could murder a certain male professor for getting too close to his dear Flayn without Lady Rhea getting too upset. Flayn, as if sensing his thoughts, smiled.  
“Don’t you think so? **She’s** so sweet and kind” She teased, giggling as he gave her a dark look. “Have you considered marriage yet?”  
“Please be more specific next time” Seteth’s sighs were drowned by Flayn’s sweet laughter.))

* * *

When Seteth heard the news, he was beside himself in worry. He searched the monastery high and low for the twins— not unlike what he did for Flayn. He found them in the graveyard, standing the same way he first saw them: The male on one side, their ‘father’ in the middle, and the female on the other. Their hands were laced together, but not with the same feeling as they had mere days ago— when they left on their last mission with Jeralt. Seteth had heard about how the two acted around Garreg Mach; just as silent as the day they arrived, holding onto each other with every step, giving pained smiles to their students as they passed, only stopping to listen to the house leaders and never responding verbally. Seteth wondered if that was how he would’ve acted had the two not risked their lives to find Flayn; if that was how he acted when he lost his _wife_. A soft hand found its way into his, and he was joined by Flayn. She looked up at him with worry in her eyes, gripping a small bundle of flowers in her free hand. Flayn gave her a tired smile before squeezing her hand back and leading her down to comfort the two.

((Byleth smiled her trademark soft smile he learned to love, and her brother grinned his own trademark scheming grin. Although the smiles didn’t reach their eyes, and he could tell they were forced, Seteth felt comforted all the same.))

* * *

When Seteth saw their hair, he nearly had a heart attack. Flayn had lead the twins into his office, yelling his name and pleading for him to come out. Based on her playful (not fearful or in danger) tone, he simply smiled to himself and waited for Flayn to impatiently open the door. When she did, she shoved the twins inside, and gave Seteth the fright of his life. Light, green hair accompanied green eyes, and while Byleth had the decency to look embarrassed about his reaction to her new colors, her brother laughed as Seteth fell out of his chair. He wasn’t sure what exactly gave him such a fright, but when pressed he attributed it all to the sudden color changes, and tried to ignore the tightness in his chest.

((That night he dreamed of a beach, of a small family of three enjoying a fish dinner; of a woman whose touch he still longed for.))

* * *

When Seteth saw them again, after five long years, his first and immediate thought was “Demons”. He immediately felt relieved. They were _alive_, all this time, just _sleeping_. It was almost funny, and he felt the same immature anger he had first felt about Byleth when he was ready to start a fist fight with the hard headed male. But seeing the twins’ eyes light up in recognition, and seeing the way Flayn threw herself at the two with tears of joy, he decided to let it go.

((He still felt a bit betrayed, he had gone beside himself in worry over loosing _more_ people he cared about. But when the twins smiled, it reached their bright green eyes, and he found he couldn’t stay mad.))

* * *

When Seteth thought of the twins, and how much he grew to care about them over the years, how much he grew to trust then, how much he grew to love them, the had one thought: “_Twins are Dangerous_”

**Author's Note:**

> Next part in the Twins_Are_Dangerous AU!  
((I said there's no ships, but I totally ship Female Byleth and Seteth))((It's not in this work cause I'm a coward))


End file.
